Calibrating Astrotrac Polar Scope

[ashworthacca]

Hi guys, last night I thought I'd check the collimation of the polar scope for my Astrotrac and it is miles out. I pointed at an object a few hundred yards away and when rotating the polar scope (in the polar scope arm on the Astrotrac) 180 degrees the view moves in a big arc and the target moves quite away. The scope needs calibrating.

I've scoured the Internet and can't really find any good guides on the best way to do it. One mentions something about a vice and 1" strips of Aluminium:confused: another says leave the scope in place on the Astrotrac but the arm is not really that sturdy.

Also, what is the procedure? I used AstroBaby's superb guide to calibrate the polar scope on my HEQ5 as that guide explained the procedure and more importantly which way and which screws to turn. Is the principal the same for the Astrotrac polar scope?

Any advice would be appreciated.

Regards

[ashworthacca]

Well this lunchtime I went home to see if I could calibrate the polar scope whilst in the Astrotrac polar scope arm. Pointed at a chimney pot a few hundred yards away with the illuminated reticle switch pointing upwards, rotated 180 degrees and messed with the 3 screws to correct half the distance of the error. Back to the original position and reposition the view to the top of the chimney pot and then same procedure. 4 goes and collimation now seems spot on in comparison to when I received it new.

Now there is a little bit of movement in the polar scope arm so I'd like something rock solid to fine tune the calibration. Any ideas for a better way to calibrate the polar scope?